Syncope is typically preceded by a sudden drop in heart rate, blood pressure or both. Without warning to the patient, a syncopal episode can pose considerable risk of injury to the patient, particularly if the patient is standing or driving a car at the time of syncope. Accordingly, it is desirable to provide the patient with some warning that syncope is likely to occur so that the patient has time to sit down, park a car, or take other actions such as specific counter-maneuvers to reduce the risk of injury and/or prevent syncope. Implantable devices that include transvenous intracardiac leads can measure heart rate and blood pressure for use in predicting syncope. However such leads are invasive and may not be required for other therapeutic or monitoring reasons in a particular patient